WPF Validation.Errors Contains Nothing

Question

I am having problems displaying the Validation.Errors in my ItemsControl. The Validation.Errors does not contain anything. I am NOT using BindingGroup but I use my own custom TextBoxes. Here is the ItemsControl code:

     <ItemsControl x:Name="errorList" ItemsSource="{Binding Path = (Validation.Errors), ElementName=gvAddCustomer}" >
                <ItemsControl.ItemTemplate>
                    <DataTemplate>                        
                                <TextBlock FontSize="18" Text="{Binding Path=ErrorContent}" />
                    </DataTemplate>
                </ItemsControl.ItemTemplate>
            </ItemsControl>

My TextBox uses the ErrorTemplate to display the errors beside the TextBox control and it displays correctly with the error message. Here is the style: 

 <Style x:Key="TextBoxStyle" TargetType="TextBox">
            <Setter Property="Validation.ErrorTemplate">
                <Setter.Value>
                    <ControlTemplate>
                        <DockPanel LastChildFill="True">
                            <TextBlock DockPanel.Dock="Right"
                        Foreground="Orange"
                        FontSize="12pt"
                        Text="{Binding ElementName=MyAdorner, Path=AdornedElement.(Validation.Errors)[0].ErrorContent}">
                            </TextBlock>
                            <Border BorderBrush="Red" BorderThickness="2">
                                <AdornedElementPlaceholder Name="MyAdorner" />
                            </Border>
                        </DockPanel>
                    </ControlTemplate>
                </Setter.Value>
            </Setter>
        </Style>

Can anyone explain why the Validation.Errors contains nothing when I bind to the ItemsControl?

Answer 1

I did my validation very similarly:

<TextBox
    Style="{StaticResource TextBoxValidationError}"
    Name="PatientFirstName" TabIndex="0">
    <TextBox.Text>
        <Binding Path="Patient.PatientFirstName" UpdateSourceTrigger="PropertyChanged">
            <Binding.ValidationRules>
                <bs:NameRequiredRule />
            </Binding.ValidationRules>
        </Binding>
    </TextBox.Text>
</TextBox>

The only drawback is that it does not fire the validation until you enter the first character. You can force it do it in the constructor like this:

System.Windows.Data.BindingExpression be;
DependencyProperty txtProp = System.Windows.Controls.TextBox.TextProperty;
be = PatientFirstName.GetBindingExpression(txtProp);
be.UpdateSource();